用nib创建view

• (UINib *)nib {
  // return [[[UINib nibWithNibName:NSStringFromClass(self) bundle:nil] instantiateWithOwner:nil options:nil] lastObject];
  // return [[[NSBundle mainBundle] loadNibNamed:NSStringFromClass(self) owner:self options:nil] lastObject];
  return [UINib nibWithNibName:NSStringFromClass(self) bundle:nil];
  }